1. Field of the Invention
The present invention relates to countermeasure flares, and more particularly to novel flare designs and assemblies for generating desired countermeasure effects, and to methods of their designing, fabricating and using the same.
2. Prior Art
A flare is typically defined, but without limitation, as a pyrotechnic device designed to produce a luminous signal or illumination. Flares are pyrotechnic devices designed to emit intense electromagnetic radiation at wavelengths in the visible region (i.e., light), the infrared (IR) region (i.e., heat), or both, or other required regions of the electromagnetic radiation spectrum without exploding or producing an explosion. Conventionally, flares have been used for signaling, illumination, and defensive countermeasures in both civilian and military applications.
An example of a conventional flare is what may be referred to as a standard illumination flare assembly that includes a single cast or pressed flare pellet that has an outside circumference and one end inhibited from burning. These flare pellets are generally ignited on one end and burn from end-to-end. These types of standard illumination flare assemblies typically have burn times that are an order of magnitude higher than decoy flares, typically ranging from tens of seconds to one or more minutes. However, in exchange for the length of the burn time, these flares typically do not exhibit sufficient magnitudes of visual light output to distract weapons operators.
Flare assemblies are utilized in various manners as defensive countermeasures. For instance, what may be characterized as “visual” flash flares have been utilized to at least generally distract, startle, and/or “throw off” a person responsible for guiding and/or aiming a missile, such as a laser guided missile, at an object, such as a tank or an airplane. A general premise behind these visual flash flares is that enough light in the visual wavelengths will be emitted via ignition of the associated payload that a person responsible for guiding and/or aiming a missile cannot help but be distracted by the magnitude of light produced.
Other prior art flare assemblies may be utilized to distract or “confuse” an infrared guided missile's guidance system into locking in on the infrared light from the flare assembly rather than the exhaust/plume of an aircraft. In this manner, flare assemblies have been utilized to decoy infrared guided missiles at least generally away from an aircraft. Decoy flares are one particular type of flare used in military applications for defensive countermeasures. Decoy flares emit intense electromagnetic radiation at wavelengths in the infrared region of the electromagnetic radiation spectrum and are designed to mimic the emission spectrum of the exhaust of a jet engine on an aircraft.
Many conventional anti-aircraft heat-seeking missiles are designed to track and follow an aircraft by detecting the infrared radiation emitted from the jet engine or engines of the aircraft. As a defensive countermeasure, decoy flares are launched from an aircraft being pursued by a heat-seeking missile. When an aircraft detects that a heat-seeking missile is in pursuit of the aircraft, one or more decoy flares may be launched from the aircraft. The heat-seeking missile may, thus, be “decoyed” into tracking and following the decoy flare instead of the aircraft.
Currently available and conventional decoy flares are generally constructed as an elongated, usually cylindrical grain that is inserted into a casing. The casing may have a first, aft end from which the decoy flare is ignited and a second, opposite forward end from which the grain is projected upon ignition. The generally cylindrical grain can include grooves or other features that extend longitudinally along the exterior surface thereof to increase the overall surface area of the grain.
The ignition system of a decoy flare conventionally includes an impulse charge device positioned within the casing and a piston-like member positioned between the impulse charge device and the grain. The ignition system may further include a first igniter material positioned on the side of the piston-like member adjacent the impulse charge device, and a second igniter material on the side of the piston-like member adjacent the grain. This second igniter material (often referred to as “first-fire” material) may surround the grain and may be disposed within the longitudinally extending grooves of the grain.
The impulse charge device may be ignited by, for example, an electrical signal. Upon ignition, the expanding gasses generated by the ignition of the charges would force the piston-like member and the grain out from the second end of the casing. The piston-like member may include a mechanism that causes or allows the first igniter material to ignite combustion of the second igniter material after the piston-like member and the grain have been deployed from the casing by the impulse charge device. The combustion of the second igniter material generally ignites combustion of the grain itself.
FIGS. 1A and 1B illustrate an example of a prior art flare 10. The flare 10 includes a grain assembly 20 shown in FIG. 1B, which is disposed within a casing 12. The grain assembly 20 includes a grain 22 of combustible material and a reactive foil 24 that is positioned relative to the grain 22 and configured to ignite combustion of the grain 22 upon ignition of the reactive foil 24. The reactive foil 24 may include alternating layers of different materials that are configured to react with one another in an exothermic chemical reaction upon ignition, which exothermic chemical reaction may be used to ignite combustion of the grain 22.
The flare 10 may be configured as a decoy flare, and the combustible material of the grain 22 may be configured to emit electromagnetic radiation upon combustion of the grain 22 with peak emission wavelength within the infrared region of the electromagnetic radiation spectrum. The flare 10 may be configured for signaling, illumination, or both, and may be configured to emit a peak emission wavelength within the visible region of the electromagnetic radiation spectrum. The flare 10 may be configured to emit a peak emission wavelength within the ultraviolet region of the electromagnetic radiation spectrum.
As shown in FIGS. 1A and 1B, both the grain 22 of the grain assembly 20 and the casing 12 may have an elongated shape. The casing 12 may have a first, aft end 14 and a second, opposite forward end 16. An impulse charge device 30 may be provided at or within the first end 14 of the casing 12 or may be coupled to the flare 10 when the flare 10 is ready to be deployed or mounted on the intended platform. The impulse charge device 30 may be configured to force the grain assembly 20 out from the second end 16 of the casing 12 upon ignition of the impulse charge device 30. As shown in FIG. 1B, the decoy flare 10 may include a piston member 32 disposed within the casing 12 between the impulse charge device 30 and the grain assembly 20. The grain 22 may include an aft end 23A and a forward end 23B. The flare 10 may further include an end cap 40 proximate to the forward end 23B of the grain 22. The grains 22 are generally cylindrical in shape with rectangular or circular cross-section, and are generally provided with a circular bore and grooves of certain shape on their exterior surfaces along the length of the grain.
In certain flares, the piston member 32 may be part of an ignition assembly (often referred to in the art as an “ignition sequence assembly,” a “safe and arm igniter,” or a “safe and arm ignition assembly”). In certain cases, the flare 10 may include an ignition assembly having a mechanism configured to prevent ignition of the reactive foil 24 and the grain 22 until the grain assembly 20 has been substantially ejected from the casing 12 by the impulse charge device 30. In other cases, the flare 10 may include an ignition assembly that is configured to cause ignition of the reactive foil 24 and the grain 22 before the grain assembly 20 has been substantially ejected from the casing 12 by the impulse charge device 30, or as the grain assembly 20 is being ejected from the casing 12 by the impulse charge device 30. For example, the ignition assembly may include a pellet 34 of combustible material that is attached or coupled to the piston member 32. The pellet 34 may include, for example, a boron- or magnesium-based material. Combustion of the pellet 34 may be initiated upon ignition of the impulse charge device 30, and combustion of the pellet 34 may cause ignition of the grain assembly 20.
FIG. 2 is a cross-sectional view of the grain assembly 20 of the flare 10 shown in FIGS. 1A and 1B taken along section line 4-4 in FIG. 1B. As shown in FIG. 2, in some flares, at least a portion of the reactive foil 24 may be in direct physical contact with and cover at least a portion of the grain 22. In these flares, the reactive foil 24 is in direct physical contact with at least a portion of at least one exterior lateral surface 28 of the grain 22. Furthermore, the reactive foil 24 may not be in direct physical contact with exterior lateral surfaces 28 of the grain 22 that define the grooves 26. In other flares, the reactive foil 24 may be in direct physical contact with and cover each exterior lateral surface of the grain 22 or alternatively the reactive foil 24 may not be in direct physical contact with any surface of the grain 22, but merely positioned proximate to the grain 22 such that combustion of the reactive foil 24 ignites combustion of the grain 22.